The invention generally relates to a seat belt pretensioning device and more particularly to a pretensioner associated with the non-buckle anchor point of the seat belt system.
A seat belt pretensioner or belt tightener, as it is also referred to in the art, is used to reduce the amount of slack in a seat belt system in relationship to the seated occupant (about whom the seat belt system is placed). one type of pretensioner or belt tightener is associated with a seat belt retractor. In this device or system the spool of the retractor is caused to rewind, thereby eliminating the slack about the occupant. In a three-point seat belt system the retractor, in its pretensioning mode of operation, tightens the shoulder belt which in turn pulls upon and tightens the lap belt which is often permitted to slip through an opening on a tongue. Another type of pretensioning system utilizes a pretensioner or belt tightener that is connected directly to the seat belt buckle. With the seat belt installed about the occupant, a tongue is inserted and latched within the buckle. It is the tongue that separates the shoulder belt portion and the lap belt portion of the seat belt. On activation, the pretensioner pulls the buckle, and hence the tongue, downwardly thereby tightening the lap belt and shoulder belt respectively about the lower and upper torso of the occupant.
Reference is briefly made to FIG. 1 which illustrates a conventional three-point safety belt system 20 as might be utilized in conjunction with the rear bench seat of an automobile. The same or similar system is utilized with each of the front bucket or bench seats in a vehicle. The three-point system 20 comprises a seat belt retractor 22 which may be mounted upon the rear shelf 24 of the vehicle. The retractor may be mounted within the back 30 of the seat 32. The location of the retractor is denoted by numeral 22'. The seat would also include a slot 34 through which the seat belt exits. The retractor can also be mounted behind the side trim of the passenger compartment. The seat belt system 20 includes a seat belt or safety belt 40 which is divided into a shoulder belt portion 42 and a lap belt portion 44. The demarcation between the shoulder belt and lap belt is defined by a tongue 46 that is inserted and locked within a seat belt buckle 48. The lap belt portion 44 (and shoulder belt portion) may be permanently secured to the tongue 46 or the seat belt 40 can be slidingly received through a slot on the tongue. A pretensioning device 50, such as shown in U.S. Pat. No. 5,667,246 and incorporated herein by reference, is secured between an anchor point 52 and the buckle 46. Characteristic of buckle pretensioners, the pretensioner 50 includes a hollow tube having a movable piston therein. The piston is secured to one end of a wire cable. The other end of the cable is secured to the seat belt buckle, or alternatively, to a short length of seat belt material. The pretensioner 50 includes a quantity of pyrotechnic material which, when activated, generates products of combustion causing the piston to move down the tube carrying with it the cable. This repositioning of the piston moves the seat belt buckle downwardly, thereby eliminating a degree of slack in the lap belt portion and the shoulder belt portion in relationship to the seated occupant (not shown).
As is known in the art, the use of a buckle pretensioner moves the buckle with a significant force and resulting acceleration and velocity. The operation of the seat belt buckle might cause a conventional buckle to open. As a consequence, blocking or balancing buckles (also referred to as "anti-g buckles") are utilized in the buckle pretensioning, high deceleration environment to prevent the latching element of the buckle from opening.
Again with reference to FIG. 1, the end 44b of the lap belt portion 44 remote from the buckle 48 is secured to a structural element such as the vehicle floor 31 (or to seat frame 30a) by an anchor 58, typically comprising a metal bracket sewn to the lap belt 44 and having an opening therein. The bracket is secured to a structural element using a threaded fastener or the like.
It is an object of the present invention to provide a belt tightening device secured to the non-buckle end of a lap belt.
Accordingly the invention comprises: a multi-point seat belt system for protecting an occupant seated upon a vehicle seat, the system comprising: a lap belt securable about the occupant with some amount of slack, a seat belt buckle attached to one end of the lap belt at an inboard location in the vehicle and pretensioning means secured to an opposite end of the lap belt for eliminating any slack in the lap belt about the occupant, the pretensioning means located at an outboard vehicle location.
Many other objects and purposes of the invention will be clear from the following detailed description of the drawings.